Hotplug
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We see that sda1 has role '''[2]'''. Since RAID1 needs only 2 components - [0] and [1], the [2] means "Spare disk". And it is '''(F)'''ailed. | We see that sda1 has role '''[2]'''. Since RAID1 needs only 2 components - [0] and [1], the [2] means "Spare disk". And it is '''(F)'''ailed. | ||
− | But why the system thinks that sda2 is still OK? | + | But why the system thinks that /dev/sda2 in /dev/md1 is still OK? |
− | Because my system | + | Because my system hasn't tried to access /dev/md1 yet (I have no data on /dev/md1). The /dev/sda2 will be marked as fault automatically as soon as I try to access /dev/md1: |
# dd if=/dev/md1 of=/dev/null bs=1 count=1 | # dd if=/dev/md1 of=/dev/null bs=1 count=1 |
Revision as of 07:33, 15 April 2010
HW issues of the disk hotplugging are described in the Hotswap chapter of theHardware issues page.
The Linux RAID supports hotplug operations fully from Hot-unplug branch of the mdadm version 3.1.2.
mdadm versions < 3.1.2
Let's have the following RAID configuration:
# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sda1[0] sdb1[1] 3903680 blocks [2/2] [UU] md1 : active raid1 sda2[0] sdb2[1] 224612672 blocks [2/2] [UU]
The md0 contains the system, md1 is for data (but is not used yet).
If we hot-unplug the disk /dev/sda, the /proc/mdstat will show:
# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sda1[2](F) sdb1[1] 3903680 blocks [2/1] [_U] md1 : active raid1 sda2[0] sdb2[1] 224612672 blocks [2/2] [UU]
We see that sda1 has role [2]. Since RAID1 needs only 2 components - [0] and [1], the [2] means "Spare disk". And it is (F)ailed.
But why the system thinks that /dev/sda2 in /dev/md1 is still OK? Because my system hasn't tried to access /dev/md1 yet (I have no data on /dev/md1). The /dev/sda2 will be marked as fault automatically as soon as I try to access /dev/md1:
# dd if=/dev/md1 of=/dev/null bs=1 count=1 1+0 records in 1+0 records out 1 byte (1 B) copied, 0.0184819 s, 0.1 kB/s
# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sda1[2](F) sdb1[1] 3903680 blocks [2/1] [_U] md1 : active raid1 sda2[2](F) sdb2[1] 224612672 blocks [2/1] [_U]
What we can do is remove the failed disk:
# mdadm /dev/md0 --fail detached --remove detached mdadm: hot removed 8:1
mdadm versions > 3.1.2
(to be finished)